Stator blade assembly for axial-flow turbines



Oct. 6, 1970 R. STRUB 3,532,437

STATOR BLADE ASSEMBLY FOR AXIAL-FLOW TURBINES I Filed June 27, 1968 .5 Sheets-Sheet 1 [JV/Ill Inventor- Ren Srru b BYGDW' ,W,

ATTORNEYS Oct. 6, 1970 R. STRUB 3,532,437

- S 'I'ATOR BLADE ASSEMBLY FOR AXIAL-FLOW TURBINES I Filed June 27; 1968 3 Sheots-Sheet ,2

Inventor- Rene" Sfrub BYW ATTQRNEYS Oct. 6, 1970 R. STRUB 3,532,437

STATQR BLADE ASSEMBLY FOR AXIAL-FLOW TURBINFfS Filed June 27, 1968 '3 Sheets-$heet 3 v lNV ENTOR gene Strub BY I 6 A ORNEYS United States Patent O 3,532,437 STATOR BLADE ASSEMBLY FOR AXIAL-FLOW TURBINES Ren Strub, Winterthur, Switzerland, assignor to Sulzer Brothers Limited, Winterthur, Switzerland, a company of Switzerland Filed June 27, 1968, Ser. No. 740,600 Claims priority, application Switzerland, Nov. 3, 1967,

15,437/67 Int. Cl. F01d 9/04 US. Cl. 415-136 Claims ABSTRACT OF THE DISCLOSURE There is disclosed a stator blade assembly for axial-flow turbines comprising inner and outer concentric rings with stator blades extending between them, the outer ring including a flange extending axially of the turbine past the rotor blades of the associated stage of the turbine. The outer ring is made up of circumferentially overlapping segments to permit radial expansion and contraction of the assembly with changes in temperature, and is also provided with a radially extending rib which fits into a groove on the inside of the turbine housing to prevent flow of the working substance past the outside of the assembly. Suitable means are provided to hold the assembly in fixed position in the housing.-

SUMMARY OF THE INVENTION The present invention pertains to a stator blade assembly for axial-flow turbines. This assembly comprises blades extending between radially inner and outer rings, and a stationary annular flange or shroud for the turbine rotor.

In accordance with the invention, the stator blade assembly is extensible in a radially outward direction, and the cover ring forms a part thereof.

BRIEF DESCRIPTION OF THE DRAWING The invention will now be further described in terms of a number of nonlimitataive exemplary embodiments by reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary axial section through a turbine including a stator blade assembly according to the invention;

FIG. 2 is an axial view in plan of the stator blade assembly of FIG. 1;

FIG. 3 is a fragmentary developed view, radially inward, of the stator assembly of FIGS. 1 and 2;

FIG. 4 is a fragmentary plan axial view of the apparatus of FIG. 3, being thus a fragmentary view at an enlarged scale of the peripheral portion of the apparatus shown in FIG. 2;

FIG. 5 is a fragmentary perspective exploded view at an enlarged scale of two adjacent segments in the outer ring of the stator blade assembly of FIGS. 1 to 4;

FIG. 6 is a view similar to that of FIG. 4, but showing another construction according to the invention; and

FIG. 7 is still another view similar to that of FIG. 4 and showing still another embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1, reference character 1 denotes generally the stator blade assembly for the nth stage of an axial-flow turbine whose rotor is generally indicated at 2. The assembly comprises a set of blades 6 extending between radially inner an douter rings 4 and 5. It also comprises a cover ring or flange constituting a shroud 7 for the rotor blades 8 of that stage. The inner ring 4 extends over 360 about the turbine axis but may be made of two parts for easy assembly as indicated in FIG. 2, where the joints between the two parts of ring 4 are indicated at 3. Slits 10 are provided at the exterior periphery 9 of the ring 4. In this way, the differences in thermal expansion between the inner and outer peripheries 11 and 9 of the ring 4 are accommodated. The inside periphery 11 has a lower temperature than the exterior surface 9 by reason of the passage, during operation of the turbine, of a coolant in the space between the inside limit 11 of the ring 4 and the outside 12 of the rotor 2 (FIG. 1).

The outer ring 5 of the stator blade assembly 1 is made up of a number of segments 13 (FIG. 2), of which three successive segments, generally identified at 14, 15 and 16, are shown in FIG. 3. Two further such segments are shown at 30 and 31 in FIG. 2. The segments are movable with respect to each other in the plane of the assembly, i.e., in the plane of FIG. 2. As appears in FIG. 3, successive segments such as the segments 14, 15 and 16 are provided with end portions or tabs 17 and 18 whose overlapping surfaces 19 and 20 engage each other in the plane of the assembly and can slide over each other. It will be recognized that the plane of FIG. 3, onto which part of the outer periphery of the stator assembly has been developed, is perpendicular to that of FIG. 2. The segments are provided with a circumferentially and radially extending exterior rib 21. This rib is received in an annular groove 22 in the inner wall 23 of the turbine housing 24, as illustrated in FIGS. 1 and 2. The rib portion of each segment includes an axial extension 21a of short circumferential extent. Between the circum-ferentially outer surfaces 25 of the ribs 21 and the bottom 26 of the groove 22 there is provided a clearance 27 in order to accommodate the radial expansion of the blade assembly 1 with increase in temperature. Rotation of the blade assembly within its plane which would otherwise occur under influence of the working substance (e.g., steam) passing through the turbine is prevented by abutments which are provided on the turbine housing at several points about its inner periphery. As indicated in FIG. 2, two pairs of abutments are thus provided. Of the first of these pairs, one abutment is shown at 28 and of the second pair one abutment is shown at 29. The abutment 28 lies between the rectangular extensions 21a of the two adjacent segments 30 and 31 of the assembly outer ring 5. The abutment 29 is similarly engaged between two segments of the ring 5.

Each segment of the ring 5 possesses a flange 33 extending axially of the turbine beyond the rotor blades 8 of the turbine stage to which that ring 5 belongs. These flanges together make up the shroud or covering ring 7 of that stage, dimensioned with suitable clearance 34 from the rotor blades 8. In the drawing, the flanges 33 have been indicated as integral parts of the segments. They can, of course, be separate therefrom and screwed or otherwise fastened thereto. The ribs 21 of the successive segments constitute together a sealing ring against the axially flowing working substance.

In place of the extensions 21a on the ring segments, there may be provided pins which fit into corresponding bores in the housing and in the segments themselves. With such a construction, the pins must be inserted from the outside of the housing.

The construction of the outer ring of the stator blade assembly of FIGS. 1 to 4 is further illustrated in FIG. 5 where two adjacent segments 14 and 15 are shown, separated from each other in an exploded view which shows the overlapping tabs 17 and 18 thereof. The surface 19 on tab 17 is visible on segment 14.

In FIG. 5 the surfaces identified by reference characters a and b on segment 15, are cylindrical surfaces coaxial in the axis of the assembly. Surfaces c, d, c and 3 d instead may be plane surfaces perpendicular to that axis. The blades 6 shown in FIG. extend radially toward the axis of the assembly. In the completed assembly, surfaces a and a are continuous and make up the surface previously referred to. The surfaces c and c also form part of a single surface, namely a plane surface, as do the surfaces d and d.

A further embodiment of the invention permitting the stator blade assembly to be fastened in position free of dilficulties attendant upon the thermal expansion and contraction of the parts is illustrated in FIG. 6. The segments which make up the outer ring of the stator blade assembly are here provided each with a eircuferentially extending foot 36. On each segment, this foot is fastened at one end, as indicated at 37, to the housing 24 in the circular groove 22 thereof, for example by means of bolts. The feet are so dimensioned as to possess the elasticity necessary to accommodate the expansion of the blade assembly. In this embodiment also, the segments may be provided with sealing ribs 21 extending circumferentially.

In the embodiment of the invention shown in FIG. 7, the blade assembly is supported by springs 39 engaged between the outer ring of the assembly (made up of segments 46) and the inner wall of the housing 24. Each spring is supported at its ends 40 and 41 in notches 42 and 43 of the housing whereas the proturberant middle part 44 of the spring is received in a notch 45 of the ring segment 46. Instead of the blade-type spring illustrated, cup-like springs may be employed.

On starting up of the turbine, the blade assembly 1 rundergoes radially outward expansion. The flange 7, which constitutes a part of the blade assembly, is consequently moved outwardly by an equal amount. Since the rotor blades 8 undergo substantially the same radially outward expansion as does the stator blade assembly, the original clearance between the flange and the rotor blades is substantially preserved. The advantage of this construction is that the turbine may be built with a small clearance 34, the equality of these expansions insuring against undesired contact of the rotor blades against the flange.

While the invention has been described herein in terms of a number of preferred embodiments, the invention itself is not limited thereto but rather the invention comprehends all modifications on and departures from those embodiments properly falling within the spirit and scope of the appended claims.

I claim:

1. A stator blade assembly for an axial-flow turbine comprising a radially inner ring having a plurality of radially inwardly extending slits in the outer periphery thereof, a radially outer ring made up of circumferentially overlapping segments, a plurality of blades extending between the inner and outer rings, each of said segments including an axially extending rotor blade covering portion and a radially outwardly extending rib adapted to be received in a groove on the inside of the turbine housing.

2. A blade assembly according to claim 1 further comprising axial extensions on said rib, and abutments afilxed to the turbine housing engaging between circumferentially adjacent ones of said extensions.

3. A blade assembly according to claim 2 wherein said extensions comprise pins received in bores in the turbine housing and in said segments.

4. A blade assembly according to claim 1 wherein each of said segments has affixed thereto an elastic supporting member adapted to be received in a circumferential groove of the turbine housing.

5. A blade assembly according to claim 1 further including resilient means engaged between each of said segments and the turbine housing.

References Cited UNITED STATES PATENTS 998,820 7/ 1911 Westinghouse. 2,282,894 5/ 1942 Sheldon. 2,488,875 11/1949 Morley. 3,427,000 2/1969 Scalzo.

FOREIGN PATENTS 852,789 10/1952 Germany. 928,746 6/1955 Germany. 881,880 11/ 1961 Great Britain. 282,822 1/1965 Netherlands.

EVERETTE A. POWELL, 111., Primary Examiner US. Cl. X.R. 

